A mechanical seal is a shaft sealing device that contains process fluids within a pump or other type of rotating equipment. There are generally three types of mechanical seals: component seals, made of several pieces; cartridge seals, made of one piece; and split seals. Cartridge seals generally are preferred over component seals because cartridge seals may be installed without significant training and may be tested before shipping to ensure reliability.
Pumps and mechanical seals are utilized by many industries and serve a variety of functions by moving process fluids throughout a plant. For example, pulp and paper manufacturing, chemical processing, petroleum, chemical and oil refining, utilities, and food processing, are among the more significant industries that utilize significant numbers of pumps and associated mechanical seals. Within a large processing plant there may be thousands of different pumps and associated seals, moving a variety of process fluids throughout the plant. The loss of any individual pump within the plant may cause a degradation in the plant output, profitability and efficiency. It also is common for a plant to be reconfigured either to process different products or to provide a work around to avoid a damaged pump. This reconfiguration may result in incompatible combinations of equipment and process fluids and an increased likelihood of failure.
Proper selection, installation, maintenance, operation and failure analysis of rotating equipment, and in particular pumps and mechanical seals, within a processing plant are factors in the reliability, productivity, efficiency and profitability of a processing plant, but are difficult. For example, the selection process of a seal involves the consideration of several factors, such as the operating conditions of the pump, the process fluid to be moved, the type of pump on which the seal is to be installed, and the environmental conditions under which the pump and seal operates. Other factors include the cost and quality of the seal and its ease of installation.
The selection process typically involves a seal or pump manufacturer""s trained sales engineers with factory support to ensure that a proper seal is selected. Several standards have been promulgated to establish guidelines for seal selection. These standards include the Society of Tribologists and Lubricating Engineer (STLE) SP-30 1990 and its updated version in April 1994, the CMA/STLE xe2x80x9cMechanical Seal Application Guidexe2x80x9d (1994), and the American Petroleum Institute (API) Mechanical Seal Standard 1994. The sales engineer typically has training in mechanical or chemical engineering and is provided by the manufacturer with at least some of the technical data corresponding to the seal or pump products. The sales engineer""s effectiveness also may relate to experience in a particular industry. For example, a sales engineer that is experienced in the petroleum industry may not be as effective as proposing solutions for a food processing plant.
Often the selection process is a manual process, prone to errors in communication and understanding between supplier and customer. In addition to communications problems, the different levels of experience among the sales engineers may lead to confusion when different sales engineers working for the same manufacturer make different recommendations based on their experience and understanding of the equipment.
Even if the selection process is accurate for given conditions, improper installation, operation or maintenance of the pump and seals may degrade the operation. A lack of trained personnel often is a factor in improper installation, operation and maintenance of a mechanical seal or pump. In particular, it is possible that a sales engineer without proper training may select an improper seal.
Performance of equipment also should be monitored. To ensure that equipment is operating with acceptable performance, a disciplined, problem solving approach to pump and seal operation and maintenance is used. This disciplined problem solving approach can be divided into eight areas.
The first area is defining an acceptable seal performance metric. By choosing a performance metric that is appropriate for an installation seal, performance can be measured and determined. A performance metric may be, for example, a federal, state, or local government regulation, e.g., limiting emissions from the seal, or the metric may be a measure of frequency or cost of failure, such as a mean time between failures.
The second area is troubleshooting the equipment in the field. Visual observations of the equipment and seal, the seal support system, the piping system, etc., can provide important information and data for later analysis. It also may be possible to provide corrective actions for solving the problem or failure without shutting the equipment down. Examples of such corrective actions include tightening gland bolts and adjusting a quench.
The third area is reviewing the current process and equipment data, along with the repair history for the equipment. This information can provide data on changing conditions that have negatively impacted seal reliability. Because the configuration of the processing plant changes often, it is difficult to maintain data about the configuration of the plant up to date. Modifications to equipment and changes to process fluids commonly occur. Processing plant reliability managers commonly do not have a convenient and timely method of determining the current state of equipment in a plant. In addition, because of the lack of information regarding the current state of equipment within the plant, the plant reliability manager often has inadequate information for cost and failure analysis. Life cycle costs (LCC) and mean time between failure (MTBF) are commonly used metrics to determine the efficiency and productivity of plant equipment. LCC involves tracking the costs associated with a particular pump and/or seal over a given period of time. MTBF involves tracking the time between failures of the particular piece of machinery. Without accurate up to date information on the current state of a piece of equipment, however, these measures cannot be computed accurately.
The fourth area is proper selection of pumps and seals. As pointed out above, seal selection generally is a technically difficult and manual process.
The fifth area is investigating the operational history of the pump and mechanical seal and related equipment. Such an investigation may reveal operating conditions that are incompatible with a seal or pump or other equipment. For example, operating conditions such as pressure, environmental or process fluid temperatures, etc. may deviate significantly from normal operating conditions. By analyzing these deviations from normal operating conditions, the cause of a failure may be determined to have been due to the operating conditions and not due to a mechanical failure. In addition to any data from instrumentation, the personnel responsible for operating the equipment may provide valuable data about any deviations that have occurred and why these deviations occurred.
The sixth area is performing seal analysis after a failure. Disassembly and inspection of a seal helps to understand the failure mode of the seal. There may be mechanical, thermal, or chemical damage to the seal. Information about the failure mode helps to understand the underlying root cause of the failure.
The seventh area is performing a root cause analysis to assign the ultimate underlying cause of the failure based on gathered failure data. The data that has been gathered is analyzed and, based on individual experience and scientific analysis, the root cause of the failure is determined.
The eighth area is implementing a corrective action plan and providing drawings, installation, operation procedures and training to personnel. Monitoring the work performed and updating the equipment databases also may be included in an action plan.
Failure analysis of a rotating equipment therefore is a complex and difficult activity. Often, the processing plant is dependent upon the seal or pump manufacturer to aid in this analysis. The involvement of a manufacturer in the analysis of the cause of a failure of equipment may lead to biased results.
There are other problems with current methods of failure analysis. Even without bias, the analysis is still dependent upon knowledge and experience of the analyst, and thus involves training and retaining personnel. Failure analysis performed in a plant also may fail to consider the pump and seal as part of a system, because a failure typically is examined as an isolated event independent of other considerations. Because of the level of human involvement in the failure analysis, the analysis tends to be experiential rather than scientific. Thus, the analysis is only as good as the experience and insight of the people involved. Without a disciplined approach to gathering data and a scientific basis for analysis, only the symptoms of the failure are addressed and not the underlying root cause of the problem.
The various limitations of the conventional mechanical seal failure analysis methods are overcome by providing a scientifically based process for gathering, synthesizing, and analyzing data relating to equipment failure. In particular, data indicating the current state of the equipment is gathered and verified prior to a failure occurring so that accurate information is available. After a failure or problem occurs, data about the problem or failure are methodically gathered to aid in the scientific determination of the root cause of the failure. In particular, visual images of failure modes are provided to the user to ensure that proper and accurate data are obtained. A user also is directed to gather other data about the failure and the system. After data relating to the problem or failure has been gathered, the data are synthesized and a scientific analysis is performed to determine the root cause of the failure or problem. These various methods and apparatus allow a non-specialist to properly identify and diagnose a failure or problem associated with a mechanical seal and pump.
After the root cause of the problem or failure in the system has been determined, the system suggests corrective actions and plans for implementing a corrective action. Installation instructions, training and safety information can be provided to the user to ensure proper execution of the selected corrective action.
A plant reliability manager also may monitor progress and verify that installation, maintenance and failure correction are performed correctly. The plant reliability manager also may track problems or failures by each individual or department to determine if additional training is needed.
In one aspect, a method for analyzing leakage in a piece of rotating equipment involves providing a user with data representative of a plurality of failure modes corresponding with the piece of rotating equipment. Data representative of at least one failure mode that corresponds to the failure in the piece of rotating equipment is received from the user. The selected data is analyzed to determine a root cause data. The root cause data is analyzed to determine corrective action data. Stored data characterizing the piece of rotating equipment is updated with data indicative of the root cause and corrective action.
In another aspect, a method is disclosed of analyzing a plant performance utilizing failure analysis data corresponding to a piece of rotating equipment. The method involves determining a responsible party for undertaking corrective action, tracking the reliability of the responsible party for undertaking the corrective action in subsequent failures of the piece of rotating equipment, tracking subsequent failures of the corrective action taken in subsequent failures of the piece of rotating equipment, determining maintenance data for quantifiably determining the reliability of the piece of rotating of equipment, and storing the maintenance data corresponding to the piece of rotating equipment.
In another aspect, a method for generating a proposal for replacement parts required to take a corrective action to resolve a failure of a piece of rotating equipment involves providing data indicative of a corrective action to be undertaken to resolve a failure in the piece of rotating equipment, providing a template for the data, creating a report by placing the data indicative of a corrective action into the template, and preparing the report for transmission is disclosed.
In another aspect, an apparatus is disclosed for analyzing a failure in mechanical seal. The apparatus comprises an equipment data module storing data indicative of a characteristic of a piece of rotating equipment, a problem/failure database storing problem/failure data indicative of a characteristic of a failure mode of a mechanical seal associated with the piece of rotating equipment, a seal failure analysis module receiving input data indicative of a characteristic of a failure of a particular mechanical seal associated with a particular piece of equipment. The seal failure analysis module is coupled to the problem/failure database and queries the problem/failure database for failure mode data corresponding to the input data and receives a query response of data indicative of a failure mode of the particular mechanical seal. The seal failure analysis module also is coupled to the equipment data module, and provides the equipment data module with data indicative of the failure mode of the particular mechanical seal to be associated and stored with the particular piece of equipment. A data analyzer is coupled to the seal failure analysis module and receives data from the seal failure analysis module indicative of a failure mode of the particular mechanical seal. The data analyzer is coupled to the problem/failure database and queries the problem/failure database with the failure mode of the particular mechanical seal and receives query response data indicative of a root cause of the failure mode of the particular mechanical seal.
In another aspect, an apparatus for performing failure analysis on a piece of equipment includes an equipment database containing data indicative of the characteristics of a piece of equipment, and a database of system failure mode data. A first data input module coupled to the database of system failure mode data receives data indicative of a failure mode of the particular piece of equipment and has an input of an observed failure data and provides a first query as to the data indicative of the failure mode of the particular piece of equipment that corresponds to the observed failure data and receives data corresponding to the first query. A second data input module provides a second query as to a condition extant in the failure of the mechanical seal and receives data corresponding to the second query results. The second data gathering module provides output data indicative of the condition extant in the failure of the particular piece of equipment. A system failure analyzer receives the data corresponding to the first and second queries and associates the data corresponding to the first and second query. The system failure analyzer selects data indicative of a failure mode of the particular piece of equipment that corresponds to the association of the first and second query results.
In another aspect, a method for providing information regarding plant reliability involves storing the information regarding plant reliability as a searchable collection of information, receiving requests for information regarding rotating equipment in the plant, accessing the collection of information to retrieve the information for the rotating equipment, and sending the retrieved information.
In another aspect, a method for directing requests for quotes regarding equipment relating to rotating equipment between plants containing the rotating equipment and sources of service, sales or manufacture, of rotating equipment involves receiving information provided by the plant defining the request for quote, accessing a database in response to the request for quote to retrieve data to prepare a quote, preparing the quote using the retrieved data, and sending the prepared quote to the plant.
In another aspect, a method for detecting design deficiencies involves receiving input data corresponding to a piece of equipment, receiving problem/failure data associated to the piece of equipment, comparing the input data with the problem/failure data and providing an indication of a positive match, providing the matched input data and the problem/failure data as an output, and storing the problem/failure data and associating the problem/failure data with the piece of equipment.
These and other aspects and advantages of the present invention are set forth in the following detailed description.